ASPX post back problems with combobox

I've created a simple ASPX page that lists records in a GridView. The records are a list of incidents and one of the columns is the ID of the person who reported the incident.

The initial page shows all records but I would like to provide a filter for the ReportedBy column. I've gotten this working by allowing the user to type in the Re开发者_StackOverflow社区portedByID in a textbox and then clicking on the submit button. This refreshes the page as expected with the filtered view.

The code for this page is as follows:

public MyPage()
{
    this.Load += new EventHandler(Page_Load);
}

protected void Page_Load(object sender, EventArgs e)
{
    if (IsPostBack == false)
    {
        DataAccessObj daObj = new DataAccessObj();
        IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(0);
        IncidentGrid.DataBind();
    }
}

protected void btnSubmit_Click(object sender, EventArgs e)
{
    int reportedById = 0;

    if (int.TryParse(txtReportedById.Text, out reportedById) == false)
    {
        reportedById = 0;
    }

    DataAccessObj daObj = new DataAccessObj();
    IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(reportedById);
    IncidentGrid.DataBind();
}

To make it more user friendly, I decided to add a dropdown box populated with the ReportedBy names for the user to select which would then be used to filter on upon clicking the submit button. The dropdown box has names as the display items but the values should still be set to the IDs.

The problem I have is that the ID number I get from the dropdown box always comes up as the first element of the list rather than the one the user selected at the time they clicked on the submit button.

The code for this page with this implementation is as follows:

public MyPage()
{
    this.Load += new EventHandler(Page_Load);
}

protected void Page_Load(object sender, EventArgs e)
{
    DataAccessObj daObj = new DataAccessObj();

    foreach (ReportedByItem repByItem in daObj.GetAllReportedBy())
    {
        ListItem listItem = new ListItem(repByItem.Name, repByItem.Id.ToString());
        combobox.Items.Add(listItem);
    }

    if (IsPostBack == false)
    {
        IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(0);
        IncidentGrid.DataBind();
    }
}

protected void btnSubmit_Click(object sender, EventArgs e)
{
    int reportedById = 0;

    if (combobox.SelectedItem != null)
    {
        if (int.TryParse(combobox.SelectedItem.Value, out reportedById) == false)
        {
            reportedById = 0;
        }
    }

    DataAccessObj daObj = new DataAccessObj();
    IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(reportedById);
    IncidentGrid.DataBind();
}

Any help would be gratefully appreciated. TIA

Keep in mind that with WebForms the Page_Load code is executed before the event handler code for the control which created the postback.

You have to populate the list in the section where postbacks flags are checked, just like you do with the grid.

if (IsPostBack == false){
    //bind the combobox
}

Otherwise, on a postback, the list will re-populate and the selection will be gone.

protected void Page_Load(object sender, EventArgs e)
{   
    if (!Page.IsPostBack)
    {
        DataAccessObj daObj = new DataAccessObj();

        foreach (ReportedByItem repByItem in daObj.GetAllReportedBy())
        {
            ListItem listItem = new ListItem(repByItem.Name, repByItem.Id.ToString());
            combobox.Items.Add(listItem);
        }

        IncidentGrid.DataSource = daObj.GetIncidentsByReportedById(0);
        IncidentGrid.DataBind();
    }
}